SUMMARY OF SIGNIFICANT OBSERVATIONS

¶All joints:

Seal damage always has associated putty blowhole Putty blowholes exist without resultant seal damage Soot blowby can occur away from a putty blowhole Frequency of O-ring damage has increased since incorporation of: Randolph putty; Higher stabilization pressures in leak test procedure; High performance motors. Randoph putty is more susceptible to environmental conditions such as humidi- ty and temperature. Can become leathery in dry conditions; Becomes extremely sticky in moist conditions and in some cases begins to disintegrate3*

¶August 20, 1985. A Thiokol interoffice memo mentioned that a Nozzle O-ring Investigation Task Force had been formally institut- ed, stating, "As you are aware, we have experienced O-ring damage on a random basis in the case field joints and prevalently in the case/nozzle joint on the Space Shuttle Booster Motors. The fre- quency had increased in recent flights. While we have not compro- mised the performance of any motor to date, the result of a leak at any of the joints would be catastrophic."

¶August 27, 1985. Flight STS 51-1 was launched, after which it was discovered that there was primary O-ring erosion in two loca- tions on the left-hand SRM nozzle joint. At the reviews for STS 51- J, which occurred on September 9, 1985, September 17, 1985, Sep- tember 19, 1985, and September 26, 1985, the O-ring erosion noted on STS 51-1 was merely itemized as, "left-hand nozzle to case pri- mary O-ring erosion within experience base." There was no O-ring damage on Flight STS 51-5.

¶August 30, 1985. One year and four months after the original drafting of Thiokol's Program Plan TWR-14359, for improvement of Space Shuttle SRM Motor Seals, the revised version of the plan was issued.

¶3b Thiokol, Roger Boisjoly, "SRM 0-Ring ErosiodPotential Failure Criticality," Memo 2870 FY 86:073,July 31,1985.³²³² Bid., p. 291. Rogers Commission Report, Volume 11, p. H-73.

¶October 1, 1985. R.V. Ebeling of Morton Thiokol submitted a weekly activities report to A.J. McDonald, Director, Solid Rocket Motor Project, with copies to J . Kilminster and others, which in- cluded the following statements:

¶Executive Summary. HELP! The seal task force is constantly being delayed by every possible means. People are quoting policy and systems without work-around. MSFC is correct in stating that we do not know how to run a development program.

The allegiance to the O-ring investigation task force is very limited to a group of engineers numbering 8-10. Our assigned people in manufacturing and quality have the desire, but are encumbered with other significant work. Others in manufacturing, quality, procurement who are not involved directly, but whose help we need, are gen- erating plenty of resistance. We are creating more instruc- tional paper than engineering data. We wish we could get action by verbal request but such is not the case. This is a red flag.

¶(See appendix V-H.)

¶October 4, 1985. Roger Boisjoly's Activity Report identified prob- lems in obtaining support from Mr. Kilminster for the 0-Ring In- vestigation Task Force.

¶October 30, 1985. STS 61-A experienced erosion of the right-hand nozzle primary O-ring to a depth of 0.075 inches over a 13 inch space at the 97 degree location. There was also blow-by past the primary O-rings in the center and aft field joints on the left-hand SRM. But these problems were not discussed at the STS 61-B SRB Board Review on November 4, 1985. However, Mr. Mulloy included a note at the Shuttle Project Board Review on November 6, 1985, "SRM Joint O-ring performance within experience base."

¶November 18, 1985. Mr. Mulloy briefed the Level 1 Flight Readi- ness Review stating, "Post flight inspection of SRM revealed hot gas erosion of primary nozzle/case joint-O-ring on right-hand SRM-Within previously accepted experience."

¶November 20, 1985. Thiokol briefing document TWR-15349, "SRM O-ring Task Force Status and QM-5" Recommendations, presented new seal design concepts and recommendations for Qual- ification Motor-5 testing on February 20, 1986.

¶November 26, 1985. STS 61-B experienced primary O-ring erosion in both nozzle joints. There was also blow-by past the primary 0- ring in the left-hand nozzle joint. These observations were noted at the STS 61-C SRB Board Flight Readiness Review on December 2, 1985.

¶December 4, 1985. At the STS 61-C Shuttle Project Board, Mr. Mulloy noted "SRM joint O-ring performance within experience base." The Commission's copy of the December 9, 1985, Marshall Center Board briefing was incomplete; however, at the December 11, 1985, Level I Flight Readiness Review, it was reported that there were "NO 61-B flight anomalies."

¶December 11, 1985. Thiokol management holds a Solid Rocket

¶Motor Flight Readiness Review for STS 51-L. No discussion of 0ring anomalies occurs.

¶December 1Z 1985. Larry Wear holds a Flight 51-L Solid Rocket

¶Motor Project Flight Readiness Review at Marshall Space Flight

¶Center.

¶January 3, 1986. The Level 111 Flight Readiness Review for Flight

¶51-L takes place at Marshall. SRB recovery system changes are the primary point of discussion. , January 9, 1986. Larry Mulloy makes his Flight 51-L presentation at the MSFC Shuttle Projects Office Readiness Review. SRB parachutes are discussed. O-rings are not.

¶January 12, 1986. STS 61-C experienced nozzle Joint O-ring erosion and blow-by and a field joint O-ring was eroded 0.011 inches over an 8 inch span at the 162 degree location. There was blow-by past the primary O-ring in the left-hand nozzle joint between the

¶255 degree and 335 degree locations. The primary O-ring in the left

¶SRM aft field ioint was eroded 0.004 inches over a 3.5 inch man at the 154 degree"1ocation.

¶Januarv 13. 1986. Marshall Space Flight Center 51-L Readiness

¶Review. Mulloy again does not mention O-ring anomalies.

¶January 14, 1986. Mulloy's Flight 51-L presentation to the Level

¶I1 Flight Readiness Review indicates there were "no 61-C flight anomalies."

¶January 15, 1986. During the STS 51-L Level I Flight Readiness

¶Review, Mr. Mulloy noted that there were "No 61-C Flight Anomalies," and that there were "NO major problems or issues."

¶January 25, 1986. According to Mr. McDonald, Mr. Mulloy mentioned that 61-C had suffered O-ring erosion "within experience base" at the STS 51-L L-1 Flight Readiness Review.

¶January 26 1986. The Orlando Sentinel printed an article titled,

¶"Bitter freeze is expected to clobber state Tuesday." 32a

¶January 27, 1986. Thiokol and Marshall personnel spend approximately three hours in a teleconference debating the effect that predicted low temperatures will have on the performance of the O-ring seals.

¶January 28, 1986. The ice/frost evaluation team visits Launch

¶Complex 39B at 1:45 a.m., 6:45 a.m. and 10:30 a.m. Meeting with

¶Rockwell personnel concluded with a decision to continue the launch countdown.

¶January 28, 1986. STS 51-L was launched at approximately 11:38 a.m. Eastern Standard Time.

SUMMARY OF CASING JOINT DESIGN

¶Issue

¶Why did the aft field joint between the steel containers that hold the Solid Rocket Motor propellant fail to contain the burning gases of the propellant during lift-off and flight operations?

¶John Wark, "Bitter Freeze is Expected to Clobber State Tuesday," The Orlando Sentinel,

¶Jan. 26, 1986,p. B-3.

¶Findings

The design of the field joint was unsatisfactory and could not reliably contain the burning propellant gases under the range of operating conditions to be expected during the lift-off and flight phases.
The O-ring materials and putty used in the design of the joint were unsatisfactory as used on the Shuttle, particularly during the winter months. Furthermore, neither NASA nor its contractor,

¶Morton Thiokol, can adequately control the quality or consistency of these kinds of materials, which are made from recipes known only by the manufacturer and which can be changed without certi- ' fication and approval.

¶Recommendations

NASA should write and issue a new and more accurate performance specification which would cover the full range of thermal and structural requirements for the Solid Rocket Motors, with an adequate factor of safety for unusually low temperatures.